Hematopoietic stem cell transplantation (HSCT) is a therapy where hematopoietic stem cells from another individual is transplanted into a patient to restore hematopoiesis and immune function, and it has been established as a mode of therapy in a broad range of blood, tumor, metabolism, and immune diseases. Post-transplantation immunosuppression therapy has made considerable progress in the last 20 years, but graft-versus-host disease (GVHD) continues to be a major, life-threatening post-transplantation complication. Despite preventive therapy using immunosuppressants, GVHD occurs in 30 to 80% of HSCT recipients (patients). Therefore, early diagnosis of GVHD, early initiation of therapy, and objective monitoring of therapeutic efficacy are needed. Moreover, current therapeutic methods do not always result in a cure, and the development of new therapeutic methods is needed. For information about the incidence, diagnosis, and treatment of GVHD, see the report by Sullivan et al. (Sullivan K M. Graft vs. host disease. In: Blume K G, Forman S J, Appelbaum F R, eds. Thomas' Hematopoietic Cell Transplantation. 3rd ed. Malden, Mass.: Blackwell Publishing; 2004:635-664).
At present, however, the diagnosis of GVHD is mainly carried out based on clinical findings such as skin rash, hyperbilirubinemia, diarrhea, etc., and no determinative biomarker exists that can distinguish GVHD from other similar complications (veinous occlusion, viral reactivation, a treatment regimen-related toxicity, and the like). Therefore, an invasive method such as liver biopsy is required for a differential diagnosis of GVHD. However, as biopsy is an invasive and subjective diagnostic method, it is desired to develop a new method that can facilitate early, accurate, and objective quantitative diagnosis of GVHD without reliance on biopsy, leading to suitable therapy for GVHD and improvement of the outcome of HSCT.
Recent advances in proteomics have provided several methods for investigating global protein expression in biological fluids and identifying a new biomarker for the disease or pathological conditions. One such method is surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS). This is a high-throughput, highly sensitive proteomic approach for isolating proteins from a body fluid with a complex composition such as plasma to generate a comparative protein profile. Petricoin et al. (Petricoin E F, Ardekani A M, Hitt B A, et al. Use of proteomic patterns in serum to identify ovarian cancer. Lancet. 2002; 359:572-577) have reported a biomarker for ovarian cancer based on proteomic analysis using SELDI. In SELDI, proteins obtained from a biological sample are allowed to selectively bind to chemically modified affinity surfaces on a ProteinChip (Ciphergen Biosystems, Fremont, Calif.), and then nonspecifically bound impurities are washed away. Next, the captured proteins are analyzed by TOF-MS to obtain a spectrum of the molecular mass of each protein (m/z) and relative concentration (intensity). Through recent studies this type of technologies have been successfully applied to the diagnosis of cancer and other diseases.
Recent reports describe proteomic analysis of body fluids from GVHD patients. In tests using human clinical samples, however, artifacts related to genetic background and the environment are unavoidable, and this has confounded the discovery of a new biomarker. This is particularly true for post-HSCT patients, who have a wide variety of pre-existing diseases, and undergo diverse conditioning regimens and GVHD prophylaxis. There have been no reports of the discovery of a useful marker based on biochemical methods including proteomic analysis. For example, Kaiser et al. (Kaiser T, Kamal H, Rank A, et al. Proteomics applied to the clinical follow-up of patients after allogeneic hematopoietic stem cell transplantation. Blood. 2004; 104:340-349) report on their investigation of GVHD markers by proteomic analysis using urine as a sample. Two proteins (a leukotriene, i.e., an inflammation mediator, and serum albumin, i.e., the most frequent protein in serum) were identified, but no GVHD-specific protein was found.
The reference documents cited in the present description are listed below. The contents of these publications are hereby incorporated by reference in its entirety. However, none of these documents is admitted to be prior art of the present invention.    Non-patent document 1: Sullivan K M. Graft vs. host disease. In: Blume K G, Forman S J, Appelbaum F R, eds. Thomas' Hematopoietic Cell Transplantation. 3rd ed. Malden, Mass.: Blackwell Publishing; 2004:635-664    Non-patent document 2: Petricoin E F, Ardekani A M, Hitt B A, et al. Use of proteomic patterns in serum to identify ovarian cancer. Lancet. 2002; 359:572-577    Non-patent document 3: Kaiser T, Kamal H, Rank A, et al. Proteomics applied to the clinical follow-up of patients after allogeneic hematopoietic stem cell transplantation. Blood. 2004; 104:340-349